More: Other states, such as Texas, have already begun working with DHS to mass-verify the citizenship status of their voters through SAVE. Election officials cite this as a reason why North Carolina should join in. The problem is, many of those states have encountered serious issues with the database.

"After running its entire voter list " more than 18 million records " through the SAVE database, the office identified 2,724 potential noncitizens registered to vote in Texas," Executive Director Sam Hayes said in a press release.

That's only 0.015% of the state's registered voters. But the real number of noncitizen voters in Texas is even smaller than that, because the SAVE database keeps making mistakes, an investigation by ProPublica and The Texas Tribune found. In Texas, the database incorrectly flagged hundreds of voters as potential noncitizens, with one county reporting an error rate of at least 14%.

Missouri had similar problems. In St. Louis County, the state's most populous county, around 35% of those initially flagged by SAVE were in fact registered at naturalization ceremonies, The New York Times reported. In Boone County, home to the University of Missouri, more than half the voters identified as noncitizens were actually citizens.